Beginning in the late-1990s, studies were showing that Monsanto's Roundup Ready soya was experiencing a 'yield drag'--and in the last four years alone, Greenpeace estimates the yield drag has cost American farmers more than $11 billion. And Monsanto's next generation of GM soya has other problems.A 1999 study led by Charles Benbrook, a former science adviser for the U.S. government, found an average yield drag of 5.3%, and in some places, the top conventional soy out-yielded Roundup Ready soy by as much as 10%.

Another pair of studies published two years later and led by Roger Elmore of the University of Nebraska supported Benbrooks findings. One of the studies showed the yield drag was between 5% and 10%, and the other linked yield drag directly to genetic engineering (not other factors).

A Lot of Roundup Ready SoyaThe U.S. is currently the world's largest soya producer, though the Greenpeace report points out that Brazil is expected to surpass the U.S. in the near future.

In 2008, U.S. farmers planted 30.6 million hectares of Roundup Ready soya, and 80.54 million metric tonnes of the crop were harvested--and 95% of all soy planted in the U.S. is Monsanto's Roundup Ready.

According to Greenpeace, the losses are a staggering -- 4 to 8 million metric tonnes of soya. To put this in perspective, the U.S. exports 3.7 metric tonnes to the European Union and 3.6 metric tonnes to Mexico each year.

Monsanto Has a ProblemThe limited introduction of Monsanto's new 'Roundup Ready 2' in 2009 aims to fix the yield drag problems of Roundup Ready. The herbicide-resistant gene in the updated GM seed has been inserted in a different place, apparently correcting the problem.

But while Monsanto says Roundup Ready 2's yield is 7% to 11% higher than Roundup Ready, a petition submitted to the U.S. Animal and Plant Health Inspection Service in 2006 indicates Roundup Ready 2 plants are 5% shorter than the same type of conventional plants.